This invention relates generally to rotary drilling rigs and more particularly to dust seals for use with drilling shafts on such rigs.
Some rotary drill rigs have a platform where the operator can stand to perform various manual functions associated with operating and maintaining the machine. The process of drilling a hole consists of rotating a bit while applying a downward force to it. The rotation and downward force is applied through a tubular element which runs from the drill rig rotary head to the bit. The tubular element must pass through the platform referred to above.
In addition, there must be some sort of dust seal in the platform to keep dust from blowing up around the circumference of the tubular element which passes through the platform.
Historically, platform dust seal designs have been passive in nature. The seals simply consisted of several layers of some flexible material. Each layer having a hole in the center and a series of radial slots to allow the bit to pass. The bit is always larger than the tubular element to which it is attached.
This arrangement would lose its effectiveness once the hole in each seal layer became worn so an annular gap existed between the layer and the tubular element. Once a gap exists dust can blow up onto the platform. Enlarging of the hole in each layer is a natural result of the dust blowing up at the seal and the rotary motion of the tubular element passing through the seal.
The foregoing illustrates limitations known to exist in present dust seals for drilling machines. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.